another jetting question

[horror1972]

Hi,

I just put K&N pods on my gs750 '78.

Wondering who has done this and can tell me what size mainjet to use, how may turns teh air screw, how many turns the pilot fuel screw and what position the needle.

I know there's a search function, but I get really confused whit all the different stories.

I'm sure I'm not the first who put pods on the bike, so the jetting should be pretty similair to my bike.

I tried a 118 main jet and the needle on the 4th clip, but I need to hold the choke on the half of it ,the pilot screw 3 turns out and the air screw 1/4 out, so I guess it's very lean??

I need a good basic setup, and after that I will go to the dynojet testcenter, but I need to get there..

[Mark M]

Hi,

I just put K&N pods on my gs750 '78.

Wondering who has done this and can tell me what size mainjet to use, how may turns teh air screw, how many turns the pilot fuel screw and what position the needle.

<snip>

I need a good basic setup, and after that I will go to the dynojet testcenter, but I need to get there..

Instead of looking for the final answer, what you should be looking for is the method used to jet a bike after all the changes. This has been posted many times by many people. Your bike should have VM carbs, so you want to find posts by Keith Krause, because he has the VM carbs dialed and is very knowledgable on them.

Given the age of your bike, don't expect your Dyno people to be very helpful. Unless you simply want the raw test data to use for your own tuning work, then it should be OK.

Mark

[doctorgonzo]

Stage 3 kit from Dyno fixed me up, though I had to go one position lower on the needle clip because it ran too rich.

[coltrain]

I tried a 118 main jet and the needle on the 4th clip, but I need to hold the choke on the half of it ,the pilot screw 3 turns out and the air screw 1/4 out, so I guess it's very lean??

I need a good basic setup, and after that I will go to the dynojet testcenter, but I need to get there..

Put in 127.5's for the main jets - wide open throttle. Try your needle on the bottom clip if 4 is poppin which is your mid throttle. Try putting your pilot fuel screws at around 1.5. Anywhere from 1.25 - 2 turns out for the pilot fuel screws. For the side air screws try 1.5 - 2 turns out. Play with it
That should get ya real close.

[coltrain]

What kind of exhaust are you running? Stock or 4 into 1 ?

[hkeni]

forget carbs....go EFI....

[TheCafeKid]

Stage 3 kit from Dyno fixed me up, though I had to go one position lower on the needle clip because it ran too rich.

They dont make Dyno kits for the 750s with VMs. They have a 1000 VM kit, but I have yet to get an answer on how far off thier kit would be for the 750. I have had to hand jet my 750, based off Kieths suggestions, and I have to say he's pretty right on. If you ONLY have pods on it, it will be just a bit different than Coltrains suggestions, as his and mine are based off pods AND a pipe. My suggestion? Needle in the forth clip from the top, try a 122ish range main ( i think its a 122.5 no?) Pilot jets should not need changed from the stock 15s. Air screws out 2, fuel screws out 1. That SHOULD give you a good baseline setting. You still may be a tad lean, maybe have to go up to a 125 main, but you wont know till you can get some plug chops in. If you are still lean on the 122.5, maybe try 1.5 turns out on the air screws. Kieths suggestions may be different, and if so, id be more inclined to go with his.

[coltrain]

I really wanna try that stage 3 jet kit for othe 1000s on my 750. There has got to be somebody who has tried this. The only thing I would need out of it is the needles. Thats alot of coin for a set of needles. I bet it works.

Ya know there are tiny little slight differences on the carbs for the 750 through 77 - 79. I remember reading that the air jets are different in 77. A couple other things too so we may very slight tiny jetting differences between the 77, 78, 79. I tried my needle on the bottom 5th richest setting with a tiny carb washer or spacer underneath to raise just a tad more and my bike liked it - I have pods and 4 into 1 on a 79GS750. Josh's bike (77GS750-cafekid) sounds like he uses 4th position down. I think that is because our carbs just a tad different.

[TheCafeKid]

I really wanna try that stage 3 jet kit for othe 1000s on my 750. There has got to be somebody who has tried this. The only thing I would need out of it is the needles. Thats alot of coin for a set of needles. I bet it works.

Ya know there are tiny little slight differences on the carbs for the 750 through 77 - 79. I remember reading that the air jets are different in 77. A couple other things too so we may very slight tiny jetting differences between the 77, 78, 79. I tried my needle on the bottom 5th richest setting with a tiny carb washer or spacer underneath to raise just a tad more and my bike liked it - I have pods and 4 into 1 on a 79GS750. Josh's bike (77GS750-cafekid) sounds like he uses 4th position down. I think that is because our carbs just a tad different.

The differences that I KNOW of in our carbs are in the slide arm assemblies. I have not cross referenced the jet/needle sizes, but i think they are the same. Where the 78 and 79 model VM26s have the brass plate and two nylon needle washers at the base of the slide actuator, my 77's needle simple has the clip, and slides up INTO the actuator arm just a tad. Indeed this could be the reason for the slight difference in needle setting as well, but im not entirely sure.

[coltrain]

[IMG]file:///C:/DOCUME%7E1/Owner/LOCALS%7E1/Temp/moz-screenshot-10.jpg[/IMG]http://free-pu.htnet.hr/medo/carbs.jpg

There is a diagram there with all the specs through the years for 76-79 GS750. I think the 77's may have a P-1 needle jet. Thats what I might need to get my mid throttle correct. It is according to engine no. and since your running a 15 pilot jet you probably have the later carbs.

[coltrain]

sorry about the lack of image there. Here is a link to the thread/image in which I am referring to above.

http://www.thegsresources.com/_forum/showthread.php?t=125018&highlight=float+1979+750

[horror1972]

another jetting question

wow,

a lot of replies,

I ordered 128 mains, 125 were not on stock.
gonna try when they're arrive.

thanks guys!!

[Texatl]

Air screws out 2, fuel screws out 1. That SHOULD give you a good baseline setting. You still may be a tad lean, maybe have to go up to a 125 main, but you wont know till you can get some plug chops in. If you are still lean on the 122.5, maybe try 1.5 turns out on the air screws.

Looking at this pic...

Where is the "Fuel Screw"????? (as I will be putting my carbs back together next week...)

[coltrain]

Hey those are CV carbs for most models 80 and older. Basscliff's website should help you out. There is a tutorial there. We are dealing with VM carbs which are on the earlier models.

[Texatl]

OK- sorry for the interruption 8-[ As you were.